The fluid torque converter used in the automatic transmission of a vehicle such as an automobile has such an important influence on the fuel economy and the power output of the vehicle that there is a strong need to develop a fluid torque converter which matches the performance of the vehicle for further improvement of the fuel economy and the power output of the vehicle.
It has been conventionally practiced to simulate such properties of a fluid torque converter as the torque ratio, the capacity factor and the efficiency by using a computer as an aid to the design of a fluid torque converter.
Conventionally, as a method for simulating the properties of a fluid torque converter, the velocity and pressure of the fluid are obtained from three-dimensionally distributed locations of the interior of the fluid torque converter by numerical analysis of fluid dynamics, and the values of torque at various parts of the fluid torque converter are computed so that such properties as the torque ratio and the capacity factor may be simulated according to such data. As another conventional simulation method, it was also proposed to compute the outflow angle at the stator vane array by using the method of discrete vortices, and conduct a simulation according to the thus obtained outflow angle and the theory of angular momentum.
However, according to such simulation methods, the properties obtained by the simulation often significantly deviate from the actual properties of the fluid torque converter obtained experimentally, and the properties of the fluid torque converter obtained by the simulation may not necessarily reflect the actual properties of the fluid torque converter.
Therefore, for optimum design of a fluid torque converter, in particular the optimum design of the vane profile, a large number of trial-and-error steps each involving the use of simulation are required, and even when such simulation is conducted by using a super computer, a considerable time is required for the entire process.
Since, in a three-element, one-stage fluid torque converter using a stator vane wheel of a commonly used type for motor vehicles in general, the fluid flow is a circulation flow in a closed space, and the configuration of the fluid passage and the vane profile are highly complicated, the precision of the computation based on such a simulation is often unacceptably low.